If there is one place in Portsmouth that is going to give you some understanding of how important Portsmouth city is to UK history, it's the dockyard. After all is is the worlds leading destination for naval heritage. To visit Portsmouth and not go to the dockyard is quite simply a crime!
The highlights are of course are HMS Warrior, and HMS Victory, and it is not until you get up and personal to these ships do you have any understanding of what they signify; I personally walked around Warrior and Victory in total awe that these beautiful ships were built so long ago with such amazing workmanship, beautiful rooms and interiors with equipment that have been preserved so well that it is hard to believe that they were working ships. The artillery just shines and when I asked the guides what it would have looked like in its day, they say very similar as you see it today, just a lot more people around and a bit more smelly...they liked to keep them busy, but personal hygiene wasn't that great!!
There are lots of other parts to the dock years including HMS M.33 (a worship from WW1) the Harbour Tours, The Royal Navy Museum, shops, workshops and a number of pop up galleries throughout the year. There is also a restaurant on site too so you can split up the day as you go around taking everything in.
In terms of location, its a 2 minute walk from Portsmouth Harbour train station and if you are coming by car, there is a carpark next door. If you want to split your days up so you have a cultural morning and a shopping / eating afternoon, you are 5 min walk from Gun Wharf Quays where you have a plethora of places to eat and fab designer outlet shops.
In terms of tickets, there are some great offers, especially on family tickets which will last you for the whole year which means you can come back time and time again. I would recommend buying them in advance and online - not only are you more likely to get a better price, you will also save yourself some time when getting in; as I am sure you imagine, during the peak season, the queues can be long.